1. Field of the Invention
This invention relates to endoscopes for use in surgical arts, and is directed more particularly to electronic endoscopes.
2. Description of the Prior Art
Endoscopes, which are instruments used to inspect cavities or openings, have found a great number of applications in medicine and other technologies. In the field of medicine, the use of endoscopes permits inspection of organs, or other biological specimens, for the purpose of inspecting a surgical site, sampling tissue, and/or facilitating the manipulation of other surgical instruments, usually with the objective of avoiding invasive and traumatizing surgical procedures.
Older conventional endoscopes used in medicine have an objective lens unit at their distal (forward) ends which transmits an image of the area forward of the objective lens unit to the proximal (rear) end of the endoscope for viewing in an eye-piece, the image being transmitted to the eye-piece via an image forwarding means in the form of a relay lens set, or an optical fiber bundle unit. In more recent years, in place of the eye-piece and at least part of the image forwarding means, it has been preferred to provide a small size solid state video imaging device, such as one constituting a CCD chip, in the imaging plane of the objective lens, and applying the output of that video imaging device via a suitable electronic transmission system to a video monitor for viewing by a user. With both types of image transmitting and viewing arrangements, a surgeon can view the displayed image and use the information conveyed by that image to manipulate the endoscope and other surgical instruments that have been inserted into the patient via another incision or opening in the patient's body. In the case of endoscopes that incorporate a solid state video imaging device, the image seen by the objective lens unit can be observed in a display provided by the video monitor, with or without magnification.
In U.S. patent application Ser. No. 08/319,886, filed Oct. 7, 1994, in the names of Koichiro Hori, et al., there are shown and described optical, electronic and mechanical components of a contemporary endoscope.
In the case of endoscopes that do not have electronics in the tube which is inserted into the patient, there are minimal problems with current leakage that might adversely affect the patient. However, in the case of endoscopes that have a solid state imaging device and/or other electronic or electrical components embodied in the insertion tube portion of the endoscope, there is the possibility of current leakage. In one form of the electronic endoscope, the insertion portion comprises a dual tube construction, with the solid state imaging device and other electronic or electrical components being mounted in the innermost tube of the dual tube insertion portion. The possibility of a patient-injuring current leakage is particularly grave in the case where an electrified instrument, e.g., an electrified cauterizing instrument, is used in proximity to the endoscope. The possibility of a patient-injuring electrical current flow when using an endoscope is a problem in need of solution.